Our overall objective is to contribute to the elucidation of the structure, function, and regulation of passive membrane transport systems for D-glucose in animal cells. Our initial goal is to identify and purify the component(s) of the D-glucose transport system of the human erythrocyte. Three approaches are proposed: purification based upon the reversible binding of a ligand with high affinity and specificity, purification based upon labeling with a photoactivated affinity-labeling reagent, and purification based upon separation of membraneous vesicles that contain the functioning transport system. If we are able to purify the transport system, we will investigate its reconstitution, lipid requirement(s), protein structure, location in the membrane, and extent of movement during the transport process. Also, we will make use of the methodologies developed in the purification of the erythrocyte system in efforts to purify the D-glucose transport system from fat cells. If we succeed, we will investigate the effect of insulin on the structure of this system.